1. Field of the Invention
The present invention relates to a digital document display method, and in particular, to a method for changing a layout or using the summary of the layout to display more information in an easily identified form.
2. Background Art
A document in a digital data form is characterized in that, unlike a document printed on paper, it can be easily copied or searched for by using a specific keyword. Thus, at present, many documents are prepared and distributed as digital data instead of being printed (hereinafter a document that is prepared and distributed in a digital data form is called a digital document). A digital document is also characterized in that the size of the document can be easily enlarged or reduced for display on the display device of a computer (hereinafter referred to simply as a display device).
To display a digital document on a display device, since the size of the screen of a display device is physically fixed, a satisfactory display area for the display of a predetermined digital document may not be available.
The enlargement/reduction of material is the display method employed in such a case. That is, the size of an area (hereinafter this area is referred to as a page) wherein digital document content is written is reduced, and when the reduced area is displayed, an entire page can be presented on a display device screen. However, when a large reduction rate must be employed because of the page size of a digital document, while an overview of the layout of a page can be obtained, because a small display font must be used, it is difficult to read the digital document content.
FIG. 15 is a diagram showing an example digital document. When both pages of a two page digital document are displayed on the 15 to 17 inch screen of a standard personal computer display device, the display font and images (the general objects, which are provided as graphics data and include tables, charts and photographs. The same applies hereinafter) must be reduced in accordance with the size of the pages until they are so small it is difficult to read written content and to visually identify images.
According to another method, used to display a digital document when a display area having a satisfactory size is not available, only part of a digital document is presented on a display screen, and a scroll bar is provided for scrolling the display range. Using this method, a user can browse through an entire digital document by arbitrarily scrolling the display area. However, according to this method, a user can obtain only a small amount of information merely by scanning a display screen, and also cannot gain an understanding of the structure of an entire digital document. Further, when a display screen provides little margin for the enlargement of a display to read an especially interesting entry, on such a screen the content is substantially unchanged, and the desire of a user to obtain more detailed information cannot be adequately satisfied.
FIG. 16 is a diagram showing the state wherein the digital document in FIG. 15 is displayed using the scrolling display method. In this case, only a portion that corresponds to an area 1501 in FIG. 15 is displayed with the images and the display font enlarged. And although this makes the displayed portion easy to discern visually, to gain an understanding of the remainder of the digital document the manipulation of a scroll bar 1601 is required.
As is described above, the display device of a computer may not provide a satisfactory display area for the display of a digital document. Conventionally, presently employed display methods provide reduced display sizes or screen scrolling; however, as is described above, when display size is reduced, reading a digital document is difficult because the characters are also reduced, and when scrolling is used, at any one time only a small amount of information is presented for reading.
Thus, a need has been expressed for a display method whereby an entire page of a digital document can be displayed and an understanding of the content or an overview of a desired portion of the document can be obtained, to a degree, without the layout of the page being greatly altered. For this, a device is required that can process digital document content and that can display the processed content in a predetermined display area.
An example display method of this type is an outline display method that ensures the structure of a digital document is clearly delineated, and that ensures, based on the structural information, an overview of the document is displayed in accordance with importance levels. The outline display method includes not only a general outline display process, for which various functions are provided by software such as word processors or editors, but also a process that uses web browsers to analyze the hierarchical structures of HTML documents, as evidenced by tags in the documents, and employs the results to alter display levels in accordance with the display areas that are available. When the outline display method, which reduces the number of sentences to be displayed without greatly changing the overall layout of a document, is used, sentences at low importance levels are defined as non-display entities and their presence is indicated by appending appropriate marks to high importance level sentences. However, this outline display method cannot cope with a case where outline information is not included in a digital document, or a case where a user wants to read only a specific area in detail, regardless of the intent of the creator of the document.
An additional display method of this type is one whereby predetermined sentences in a digital document are summarized. Thus, since instead of the original sentences summaries are used and displayed, the number of sentences required for a display is reduced, without affecting the overall layout of the document.
According to one conventional summarization method, a summary is prepared merely by using information, such as the structure of a sentence, extracted from the digital document. Therefore, both portions that have already been browsed by a user and portions that are yet to be browsed are regarded as contents having the same importance level, and are used to prepare a summary. However, when as much as possible of the information desired by a user is to be packed and used in a summary for a display area having limited space, while taking into account the user's browsing progress, a flexible summarization process is preferable. For example, when the size of the display area for a summary is altered, and the summary must be recreated based on the new area size, a method that reduces the volume of the contents that are currently being displayed (i.e., that have already been browsed) and creates a summary that includes new information would be preferred. As described above, however, according to the conventional summarization method, since the references for the selection of information to be used to prepare summaries is fixed, a flexible summarization process cannot be used.